Let’s Talk About Sex….

Chapter 16:

The Reproductive System

I. Anatomy of the Male and Female Reproductive SystemA. The primary sex organs, or gonads, are the testis in males and the ovaries in females. These organs produce gametes or sex cells. For males, this is the sperm, for females the ova or eggs.B. The Male Reproductive System

1. Testes- olive sized male reproductive organ which has both an exocrine (sperm-producing) and an endocrine (testosterone –producing) function. The testes contains seminiferous tubules which function as sperm-forming factories.2. Duct System within the Testes includes the epididymis, ductus deferens (vas deferens) and the urethra.

a. Epididymis- highly coiled tubes found on the superior part of the testis. It functions to mature and store sperm cells for at least 20 days. It also expels sperm with the contraction of the muscles in the epididymis to the vas deferens.

b. Ductus Deferens (Vas Deferens)- carries sperm from the epididymis to the ejaculatory duct which unites with the urethra. This passes over the bladder and moves the sperm by peristalsis. Many men will choose to have a vasectomy later in life. This procedure involves cutting of the vas deferens at the level of the testes to prevent transportation of sperm. Sperm are still produced but can no longer reach the exterior of the body; they simply deteriorate and are absorbed by the body.c. Urethra- extends from the base of the urinary bladder to the tip of the penis. It carries BOTH sperm and urine. Sperm will enter the urethra from the ejaculatory duct.

3. Accessory glands and semen- a. seminal vesicles- located at the base of the bladder and produce a thick, yellowish secretion which makes up 60% of semen. The fluids include fructose (sugar), vitamin C, prostaglandins, and other substances that nourish and activate sperm.b. Prostate gland- encircles the upper part of the urethra and secretes a milky fluid that helps to activate sperm. This fluid produced enters the urethra through small ducts. The prostate tends to hypertrophy as men age which strangles the urethra making urination difficult.

• c. Bulbourethral glands- pea-sized glands inferior to the prostate. This gland produces a thick, clear mucus that helps to cleanse the urethra of acidic urine. The mucus also serves as a lubricant during sexual intercourse.

• d. Semen- a mixture of sperm and accessory gland secretions. Fructose provides energy for the sperm cells, the alkalinity of semen helps neutralize the acidic environment of the vagina, and other elements of the semen enhance sperm motility.

4. External Genitalia include the scrotum and the penis a. Scrotum- a divided sac of skin that hangs outside the abdominal cavity. The scrotum provides the testes with a temperature that is below body temperature (about 3 degrees lower).b. Penis- The penis is designed to deliver sperm into the female reproductive tract. Regions of the penis include the shaft, the glans penis (enlarged tip) and the foreskin (prepuce). The foreskin is usually surgically removed shortly after birth by a procedure called circumcision.-Internally the spongy urethra is surrounded by three elongated areas of erectile tissue, a spongy tissue that fills with blood during sexual excitement.

5. Spermatogenesis (sperm- production)- begins during puberty and continues throughout life. This process occurs in the seminiferous tubules. a. The process of spermatogenesis involves meiosis to produce haploid sperm cells. The process takes about 64 to 72 days.b. Sperm cells are the only flagellated cell in the human body. There are three regions; the head (which contains the DNA and is covered with the acrosome containing enzymes that help the sperm penetrate the follicle cells surrounding the egg), midpiece and tail. c. The hormone FSH (follicle stimulating hormone) causes the production of sperm, and LH (Leutinizing Hormone) activates the testosterone producing cells.

6. Testosterone Production- The most important hormone produced in the interstitial cells of the testes.

a. Testosterone stimulates reproductive organ development, underlies sex drive, and causes secondary sex characteristics ( deepening of voice, increased hair growth, thickening of bones, enlargement of skeletal muscles.

C. The Female reproductive system1. Ovaries- the almond-sized primary

female reproductive organs. Ovaries produce both an exocrine product (eggs or ova) and an endocrine product (estrogen and progesterone).

a. Ovaries contain sac like structures called ovarian follicles. A follicle contains an oocyte (immature egg) surrounded by layers of follicular cells. Ovulation occurs when the matured egg is ready to be ejected from the ovary.

1) Suspensory ligaments secure the ovary to the wall of the pelvis, and the ovarian ligament secures the ovary to the uterus.

• 2. Fallopian tubes- 4 inch long tubes extending medially from an ovary into the superior region of the uterus. They receive the ovulated oocyte and provide a site where fertilization can occur.

• a. The Fallopian tubes are not physically attached to the ovary. The fimbriae are the fingerlike projections at the distal end that receives the oocyte. Cilia inside the fallopian tube slowly move the oocyte towards the uterus (3-4 days). Fertilization occurs inside the fallopian tubes.

3. Uterus- located between the urinary bladder and the rectum. In a woman that has never been pregnant it is about the size and shape of a pear. It is a hollow organ that receives, retains and nourishes the fertilized egg. Regions of the uterus include the body (major portion), the fundus (area where uterine tube enters) and the cervix (narrow outlet that protrudes into the vagina).

a. The wall of the uterus is thick and composed of three layers: Endometrium- the inner layer that allows for implantation of a fertilized egg, is sloughed off if no pregnancy occurs. The myometrium is the bulky middle layer that is made of smooth muscle and plays an active role by contracting during the delivery of a baby. The outermost serous layer is the perimetrium or the visceral peritoneum.

4. Vagina- extends from the cervix to the exterior of the body. The thin walled tube is 3 to 4 inches long. It serves as the birth canal and for menstrual flow to leave the body. The distal end of the vagina is partially closed by a thin fold of mucosa called the hymen. The hymen may be ruptured during the first sexual intercourse or during a sports activity, or various other activities.

5. External Genitalia, also called the vulva, includes the mons pubis, labia, clitoris, urethral and vaginal orifices.

a. mons pubis- fatty rounded area where pubic hair existsb. labia- two delicate elongated hair-free folds of skinc. clitoris- small protruding structure that corresponds to the male penis. It is hooded and composed of sensitive erectile tissue that becomes swollen with blood during sexual excitement. d. urethral orifice- is inferior to the clitoris and superior to the

vaginal orifice.

6. Oogenesis- the process of producing female gametes (eggs) using the process of meiosis.a. The total supply of eggs for a female are present at birth. The ability to produce eggs begins at puberty under the direction of hormones. A female’s reproductive ability declines and ends in a period called menopause.b. Primary oocytes are inactive until puberty. The hormone FSH (follicle-stimulating hormone) causes some primary follicles to mature. The LH hormone (leutinizing hormone), is responsible for causing ovulation (release of the egg from the ovary). c. Meiosis is completed after ovulation only if a sperm penetrates the egg.

7. Hormone Production by the Ovariesa. Estrogen- produced by the growing and mature follicles, also cause the appearance of secondary sex

characteristics in a young woman such as; enlargement of accessory organs, breast development, Axillary and pubic hair, fat deposits in hips and breasts, widening of pelvis, onset of menstrual cycle.

b. Progesterone- produced by a glandular structure of the ovaries called the corpus luteum (exists after ovulation). Progesterone production continues until LH diminishes in the blood. This hormone is very important in maintaining pregnancy. Many miscarriages are believed to be caused by declining levels of this hormone.

II. Mammary GlandsA. Mammary glands are present in both sexes, but normally function only in females. The role of these glands is to

produce milk to nourish a newborn baby. B. The mammary glands are actually modified sweat glands that are part of the skin. They are stimulated by hormones

(estrogen) to increase in sizeC. Anatomy of the mammary gland:

1. Areola- central pigmented area of the breast2. Nipple- protruding central area of areola3. Lobes- internal structures that radiate around nipple4. Alveolar glands – clusters of milk producing glands within lobules5. Lactiferous ducts – connect alveolar glands to nipple

III. Stages of Pregnancy and DevelopmentA. Accomplishing Fertilization- Sperm must make their way to the ovulated oocyte in the fallopian tubes for fertilization to occur (this journey to the egg usually takes 1-2 hours).

1. The oocyte is viable for 12-24 hours after ovulation2. Sperm are viable for 12-48 hours after ejaculation has occurred.

a. Once the sperm reach the oocyte their acrosomes rupture, releasing enzymes that break down the “cement” that holds the follicle cells together around the egg

B. Mechanisms of Fertilization1. Membrane receptors on an oocyte pulls in the head of the first sperm cell to make contact. The membrane of the oocyte does not permit a second sperm head to enter.2. The oocyte then undergoes its second meiotic division.3. Fertilization occurs when the genetic material of a sperm

combines with that of an oocyte to form a zygote.C. The Zygote

1. The zygote is a result of the fusion of DNA from the sperm and egg. 2. The zygote then undergoes rapid mitotic cell division. This is still occurring in the fallopian tubes as the zygote continues to move towards the uterus.

D. The Embryo1. The developmental stage that begins at cleavage (early stage of rapid cell division).2. The embryo enters the uterus at the 16-cell stage.

E. The Blastocyst Stage1. A ball-like circle of about 100 cells that begins to secrete human

chorionic gonadotropin (HCG) to produce the corpus luteum to continue producing hormones. HCG is the hormone that is detected in a pregnancy test.

2. The late blastocyst implants into the uterine wall by day 14.F. Development after implantation

1. Projections of the blastocyst called chorionic villi develop which cooperate with the mother’s uterine tissue to form the placenta.

2. Once the placenta has formed the embryo is surrounded by amnion ( a fluid-filled sac). The placenta functions to form a barrier between the mother and the baby. It delivers nutrients and oxygen to the

embryo and helps to remove wastes form the embryonic blood. No blood is exchanged (see pages 349-350 to understand fetal circulation). The placenta also becomes an endocrine organ taking over for the corpus luteum and produces estrogen, progesterone, and other hormones.

3. Finally the umbilical chord forms to attach the embryo to the placenta.

G. The Fetus1. All organ systems are formed by the beginning of the eighth week.2. Activities of the fetus are growth and organ specialization.

H. Stages of Labor- Get this baby out!!1. Dilation- the cervix becomes dilated, uterine

contractions begin, the amnion ruptures (“water breaks”)2. Expulsion- infant passes through the cervix and vagina, generally head first. If the baby is breech (rear end first) usually a c-section is needed.3. Placental stage- finally the last thing is the delivery of the placenta- you can even cook and eat the placenta because it’s full of nutrients. Yummy!

No Sex…Mmm_K